Absorbable Organic Halogen Compounds - AOX

The quantity of organic chlorine compounds contained in an effluent and produced as the result of a chemical reaction between chlorinated compounds and residual lignin from the pulp bleaching process.

Acid Free

Acid-free papers are manufactured in an alkaline environment, which prevents the internal chemical deterioration of the paper over time. The calcium carbonate being added as a buffer also makes the paper resistant to the effects of an external acidic environment.

Antique finish

Bulky, high quality, especially opaque paper with a coarse surface finish created by reducing pressure at the wet presses on the paper machine and with little or no calendaring.

Ash content

Quantity of the residue that remains after a paper sample has been incinerated at a constant weight under controlled conditions, in such a way as to ensure that all combustible material is eliminated. The ash is the result of the mineral filler contained in the paper

Archival paper

Acid-free paper made to resist deterioration for documents that must last.

B

Bagasse pulp

Pulp obtained by a chemical process from bagasse, which is the residue left over after the extraction of juice from sugar cane.

Basis weight

The weight of one ream (500 sheets) of paper cut to the size that is the industry standard for that grade.

Bible Paper

Very thin paper for printing. Originally designed specifically for printing bibles. Nowadays this type of paper is also used for commercial purposes as dictionaries and diaries in which a large number of pages is required with minimal overall volume. Also known as India paper.

Biodegradable

A substance that decomposes by the activity of bacteria and other organisms.

Blade coated paper

Paper coated using a process in which the recently applied coating is homogenised and any excess material removed by a thin, flexible metallic sheet applied to the coated surface.

Blanket

Fabric-reinforced sheet of rubber used on offset presses to transfer the impression from the plate to the paper.

Blanket cylinder

The cylinder in an offset press that sits between the plate cylinder and the impression cylinder. The inked image is transferred from the plate to the blanket, and then from blanket to paper.

Bleed

Extension of the print area of an image past the trim line of the finished printed piece. A full bleed document is printed on a larger sheet and is trimmed to size, since ink or toner would foul press cylinders or belts if it actually extended off the edges of the paper. Printers usually charge more for bleeds because more paper is required.

Blind Embossing

A technique in which a raised design is created by pressing a sheet of paper between a die and a counterplate. No ink is used.

Bond

Paper characterized by a rough, non-glare surface that accepts both printing and writing inks. High quality bonds are made from rag fibers and exhibit a characteristic snap or "rattle" when shaken.

Brightness

A measure of the light reflecting capability of a given sheet of paper. Not necessarily related to colour or whiteness. A paper with a brightness of 98 is an extremely bright sheet with almost all light being reflected back to the viewer. Bright white papers illuminate transparent printing inks, giving cleaner, crisper colour, and contrast blacks.

Brush coating

Method of coating paper in which the coating is distributed and smoothed with brushes, some of which are stationary while others are drawn across the surface.

Bulky paper

Paper that gives the impression of being thicker in relation to its grammage.

C

Caliper

Caliper is a measure of paper thickness under specified conditions expressed in thousandths of an inch. The micrometer is used to measure caliper.

Chain lines

Watermarks in laid paper that run parallel to the grain.

Chemical pulp

Fibre pulp made from chemical products that dissolve the binding agent (lignin) contained in wood. The chemical pulp process produces all the energy required by burning the substances dissolved in wood and recovering and regenerating chemical products.

Chlorine-free paper

Papers made from pulps that have been bleached with agents, like oxygen, other than chlorine.

CMYK

Cyan, Magenta, Yellow and Black, are the process colours of toner or ink used in offset and digital printing. The colours overlap and appear to mix visually to reproduce a complete spectrum of colours.

Coated paper

Made with a surface coating, which allows for maximum smoothness and ink holdout in the printing process. Coated papers are available in a range of finishes from dull to matte, and gloss.

Cockle

A wavy or puckery paper surface, with a feel and look similar to that of early pole-dried paper.

D

Dandy roll

A cylinder used in papermaking to form a watermark in the sheet as it is being formed. Also used to produce a wove or laid effect.

Debossing

The same as embossing, except that the design is pressed down into the paper, rather than raised.

Deckle-edge

An untrimmed feathered edge on the sheet of paper, created during manufacturing.

Densitometer

Instrument used to measure printed ink density to determine consistency throughout a press run.

Die

A plate or cutter, generally made of copper, brass or steel, into which an image may be carved, machined or etched. Used in die-cutting, embossing and hot foil stamping.

Die-cutting

Mechanical press operation in which a die with a sharp cutting edge is used to punch a shape out of a sheet of paper.

Digital papers

Papers designed for the specific processes of the emerging digital printing technologies. Unlike traditional offset printing, the digital environment is centered in quick turnarounds, short runs, and the ability to vary printed information within the run.

Digital proofing

Proofing directly from digital files, as opposed to using film to create proofs.

Dimensional stability

A sheet of paper's ability to maintain its exact dimensions under various printing operations and changes in humidity.

Direct to plate

A process in which printing plates are imaged from a digital file instead of film; this process can take place on the press.

dpi

The dots per inch an output device is capable of producing, or the measurement of dots per inch in a particular image. An industry standard rule of thumb is the input dpi is approximately twice the output lpi. For example 133 lpi = 266 dpi

Dry end

Part of the paper-making machine in which the web enters into contact with a series of vapour-heated drying cylinders.

Duotone

Two-colour halftone reproduction from black and white original.

Duplexing

The ability of a press or printer to print on both sides of a page without having to manually turn the sheet over.

E

ECF

Elemental chlorine free. Pulp bleached using chlorine dioxide (a salt) rather than with the more reactive chlorine gas.

Embossing

A technique in which a raised image is created in a sheet of paper by pressing the sheet between a die and its counter and applying heat.

Engraving

Printing operation in which an image is etched into a printing plate. The plate is inked and wiped clean, leaving ink only in the image areas. When paper is pressed against the plate, it is displaced slightly into the recessed areas, picking up the ink and forming an embossed effect.

F

Felt side

The "top" side of the paper sheet as it is formed in the paper-making machine. Usually the preferred side for printing.

Fine paper

Paper made mainly from fibre which is usually at least 10% mechanical pulp. High quality paper for printing and writing.

Foil

A film-like material that adds a metallic sheen or colour to paper, through a technique known as hot stamping.

Folio

In paper making, the term for full-size sheet of paper, e.g. 24x34" or 26x40". In printing it refers to a folded sheet (2 leaves - four pages). Also a term for page numbers.

Formation

Refers to the uniformity and distribution of fibres within a sheet of paper. In a well-formed sheet, solid ink coverage will go down smoothly. A poorly formed sheet will exhibit a mottled appearance when printed. Formation can be checked by holding the paper up to a light source. A well-formed sheet appears uniform, while in a poorly formed sheet the fibres appear as clumps, giving it a cloudy look.

G

Grain Direction

As the paper web is carried forward on the machine, the majority of fibres orient themselves in the machine direction. When the web of paper is sheeted, the sheets will be grain long (fibres that run parallel to the long side of the sheet) or grain short (they run parallel to the short side). Grain direction should be considered during the design process for best result during printing, folding, and converting. In sheetfed printing, paper is generally printed grain long. Folds are smoother if they go "with the grain".

Gripper

The area of a sheet of paper used by the press to hold the sheet in position.

H

Hard wood pulp

Pulp obtained through diverse processes from hardwood trees. Fibres are generally shorter than in softwood pulp.

Halftones

Reproduction of continuous tone images by means of a screen that converts the image in a pattern of tiny dots.

Hot stamping

A production process that uses heat and pressure to transfer foil to a paper's surface. The stamping die, foil and paper are pressed against a hard, flat surface. If an embossing effect is desired, a relief counter is used.

Hydrogen peroxide bleaching

Method by which the pulp is bleached in an alkaline atmosphere with hydrogen peroxide, oxygen being sometimes used also for reinforcement purposes. The method significantly reduces the need to use additives containing chlorine during the final chemical pulp bleaching process.

I

Ink absorption

The extent and rate by which a printing ink penetrates a sheet of paper.

Ink holdout

The measure of the paper surface's resistance to ink penetration. The more resistant the surface, the more the ink dries by oxidation rather than absorption.

Ink jet

A type of printer that sprays droplets of ink onto paper to form an image. Continuous inkjet printers spray a continuous stream of ink which is electronically controlled to print an image. Drop-on-demand inkjet printers shoot out single drops of ink as needed.

J

K

L

Laid

A linear pattern which is applied by a dandy roll while the paper is still very wet, to mimic the effect of some hand-made papers. The laid dandy roll is comprised of wires that run parallel to the roll's axis (laid lines), and chain lines, which connect the laid lines and run in the grain direction.

Laminated

Paper made by fusing two lighter weight sheets together to create a new sheet of desired thickness. The resulting paper is especially strong.

Laser

Acronym for Light Amplification by Stimulated Emission from Radiation. An intense, focused beam of light used in many imaging systems to produce images through electronic impulses.

Laser printer

A desktop printer which uses a laser beam to create an image on a photoconductive drum. Dry toner is attracted to the charged area and is fused to paper with heat and/or pressure.

Letterpress

Method of printing in which raised metal is inked and then pressed against the printing paper.

Long grain

lpi

M weight

The weight (in pounds) of 1000 sheets of a paper cut to the size being shipped.

Mechanical pulp

Ground material used to make pulp using exclusively mechanical energy. Almost 100% of the raw wood is used to produce this pulp. The process consumes a large amount of electricity, much more than the chemical pulp manufacturing process. In general, mechanical pulp is bleached with peroxide. Paper made from mechanical pulp acquires a coffee tone over time.

Moisture content

The amount of moisture found in a sheet of paper. If the moisture content in a sheet is too high or too low, the paper can curl or build up static, which affects the way it runs through a press, printer or copier.

N

O

Offset lithography

Printing method using a plate with an image area treated to attract ink and repel water, and a non-image area in which the reverse is true. The inked image is offset onto an intermediate blanket which, in turn, prints the image on the paper.

Offset paper

Uncoated paper designed for use in offset lithography. Important properties include good internal bonding, high surface strength, dimensional stability, lack of curl, and freedom from foreign surface material.

On-demand printing

Term for new business developing around short-run colour printing. Small quantities of high quality colour printing can be delivered "on demand" wherever and whenever required.

Opacity

Measure of the percentage of light passage through a sheet of paper. The more opaque a paper is, the less show-through there will be from printing on the sheet below. Generally, opacity and brightness are inversely related to each other: the brighter the paper, the less opaque.

Optical brighteners

Also known as fluorescent dyes, these are used extensively to make very high bright, blue-white papers. They absorb invisible ultraviolet light and convert it to visible light on the blue/violet end of the spectrum.

Out turn

Sheet of paper that serves as a reference sample for the mill or customer.

Oxford finish

PCF

Process chlorine free. A term currently used to define paper made from a combination of chlorine free (TCF) virgin pulp and recycled fibre that is de-inked using a non-chlorine bleach such as oxygen or peroxide.

Perfect binding

Bindery method where all pages are trimmed to single sheets. They are clamped together and a cover is wrapped around the spine. The pages are attached to the cover using an adhesive.

Permanent Paper

Paper completely free from mechanical wood pulp or unbleached fibre. It is usually neutral or alkaline sized and contains calcium carbonate as a filler. It is important to monitor the pH value and the alkali reserve. It is used for printing books and other similar permanent applications.

pH value

Degree of acidity or alkalinity measured on a scale of 0 to 14 with 7 being the neutral point. pH is important in paper permanence but also in proper functioning of fountain solutions in offset printing. Values lower than 7 indicate greater acidity, and values higher than 7 indicate greater alkalinity.

Picking

Picking of the surface during manufacture or printing. Picking occurs when an external stress whose value is greater than the paper's cohesion is applied to the surface.

Point

In measuring type, 1 point is 1/72 of an inch. In measuring the thickness of paper stock, a point is 1/1000 of an inch. 10-pt card stock, for example, is 10/1000 or 0.010 in.

Porosity

The measure of a sheet of paper's permeability to air. Relates to the degree of ink penetration the sheet allows and its drying ability.

Print on demand

The ability to print only the documents you want in the quantities you want, when you want.

Q

R

Rag paper

Paper made from pulp containing a high percentage of rage material, mainly cotton and recycled fabrics. The minimum percentage of pulp required for a paper to be considered rag paper varies from country to country.

Raster

An electronic file type which mathematically describes points on a grid. Also called bitmap. The finer the grid, the higher the resolution, and the larger the file size. Low-resolution files are smaller in file size than high-resolution files.

Raster image processor (RIP)

A device which interprets a page description language (such as Post Script) that contains a file's instructions for printing a page. The RIP converts the instructions into dot patterns that the printer can create to image a page.

Ream

500 sheets of paper.

Registration

Placing two or more images into alignment on press. An image that is "out of register" has some of its colour or black layers out of alignment.

S

Saddle stitch or saddle-wire binding

Industrial stapler is used to insert a staple or two into the centerfold of a signature to produce a book or brochure.

Slitting

Longitudinal division of a paper web into two or more smaller reels. This operation is often carried out in converters.

Set-off

Transferring or smearing of ink from freshly printed press sheets to another surface. Printers often add a varnish or aqueous coating in line to avoid set off of printed sheets in bindery operations.

Short grain

The grain in a paper web is naturally aligned in parallel with the direction of movement on the surface of the formation. When paper is cut, the grain may be parallel to the long side of the finished sheet (in which case it is called long grain) or the short side of the finished sheet (short grain).

Signature

Section of a book obtained by folding a sheet of paper into 4,8,12,16 or 32 pages. Signatures always contain increments of four pages.

Silkscreening

A printing method in which ink is pressed through a silk screen and mask to form an image on the printing surface.

Sizing

Substances such as starch added during papermaking to improve the printing qualities of the finished sheet.

Smoothness

The surface quality of a sheet of paper, related to the flatness of the sheet. Smoothness affects ink and toner receptivity. Smoothness is measured by the Sheffield scale. A higher value indicates a rougher sheet.

Softwood Pulp

Spiral binding

Wire in spiral form is inserted in specially drilled holds along the binding edge.

Sheffield

Finish is the smoothness of the paper surface. The Sheffield Smoothness test measures the amount of air that escapes when a Sheffield tester is pressed flat against the paper and air is blown out. The less air that escapes, the smoother the paper is. Therefore, the lower the Sheffield Smoothness, the smoother the paper is.

T

TCF

Paper that is manufactured with totally chlorine-free (TCF) fibre. Alternative bleaching agents for wood fibres include oxygen, ozone and oxygen compounds, or a combination of these processes. To be classified as TCF, chlorine cannot be used in the papermaking process or in pulp production.

Tensile strength

The greatest stress that a piece of paper is able to withstand under the conditions defined in the standard testing method.

Thermography

A mechanical process in which a raised image is formed on a sheet by dusting the paper with a resinous powder while the ink is till wet, then baking it, causing it to fuse and harden.

Toner

Tiny plastic resin particles that are used in the electrophotographic printing process to form an image. Toners can be dry or liquid. For both types, the toner particles are charged and applied to the image area on a photoconductive drum or looped belt. Then it is applied and fused to paper.

Translucent paper

Paper made by beating the paper fibres until they are very short and translucent. Some translucent papers are transparentized using chemical treatments. Translucent paper provide interesting visual contrasts and have been used successfully in a wide variety of applications.

Trap

How well a printed ink can accept the next ink printed compared with how well blank paper accepts that ink. The thickness of ink application; the drying time of that ink; the printing ink sequence; and the settings of the press all affect trap.

Trapping

The process of overlapping two adjoining colours in an image so that holes are not left in the image by the normal registration variations of the printing process.

U

Uncoated paper

Paper manufactured with no surface coating.

V

Variable imaging/data

Printing or the ability to print different text and/or images on each sheet of paper that runs through a printer or press. Both the press and the software driving it must be able to offer this capability in order for the process to work.

Volume Basis

Expression used mainly in connection with paper designed for use in books to denote the theoretical thickness in millimetres of 100 sheets of a certain grammage. The volume basis value therefore gives a rough idea of the volume or bulk of the paper.

W

Watermark

A permanent, integral pattern in a sheet of paper created during papermaking.

Web Press

A printing process or printer that is fed with a continuous reel of paper.

Wire side

The "bottom" side of paper as it is made, which may show a pattern formed by the screen that carried the paper pulp.

Woodfree

Paper that does not contain mechanical wood pulp.

Wove

Plain surface paper. The opposite of Laid, it refers to the wire pattern created by "wove" dandy roll without chain lines.

X

Xerography

An electrophotographic process that electrostatically charges an image on a photoconductive drum or belt. The charge attracts toner, which is then fused to paper.